Re: [Xen-users] Question: Best option to run an Arch Linux DomU

["Fajar A. Nugraha" <fajar@xxxxxxxxx>]

On Tue, May 11, 2010 at 8:41 PM, Mike Viau <viaum@xxxxxxxxxxxxxxx> wrote:
> I came across a wiki page from the Arch Linux guys and kick myself because
> for their Dom0 documentation references Xen 2 binaries
> (xen-2.0.7-install-x86_32.tgz)
>
> http://wiki.archlinux.org/index.php/Xen_Install

They did give a warning that "This article or section is out of date." :D

> Well I have no doubts (unless misinformed) that Arch Linux should run as PV
> domU becasue I was told due to there rolling release mentaility they are
> usually using the most up-to-date package. So in the sense of the Linux
> kernel they are using the 2.6.33 branch which has domU support already.

That depends. While the kernel supports it, it might not be enabled in
the config.
For example, Ubuntu Karmic's 2.6.31-20-server kernel has these options
enabled which allows it to run as domU kernel

CONFIG_XEN=y
CONFIG_XEN_MAX_DOMAIN_MEMORY=32
CONFIG_XEN_SAVE_RESTORE=y
# CONFIG_XEN_DEBUG_FS is not set
CONFIG_XEN_BLKDEV_FRONTEND=m
CONFIG_XEN_NETDEV_FRONTEND=m
CONFIG_XEN_KBDDEV_FRONTEND=m
CONFIG_HVC_XEN=y
CONFIG_XEN_FBDEV_FRONTEND=m
CONFIG_XEN_BALLOON=y
CONFIG_XEN_SCRUB_PAGES=y
CONFIG_XEN_DEV_EVTCHN=m
CONFIG_XENFS=m
CONFIG_XEN_COMPAT_XENFS=y
CONFIG_XEN_SYS_HYPERVISOR=y

>
> Can you give me some examples on what you mean by "then do some
> modifications"?

One example, the console will change to hvc0 (for newer kernels) or
xvc0 (on older kernel-xen). The disk would also be recognized as xvda
instead of sda. And the required disk/network modules will change as
well. See  http://pastebin.com/f6a5022bf for example on converting
Centos domU.

>
> Lastly I don't understand the domU configuration offered by the Arch Linux
> Xen page:
>

To understand Xen domU config, it'd probably be easier to install a
distro that comes with Xen builtin (Centos, opensuse) and do one of
these:
- look at examples on /etc/xen/xmexample*
- create a domU using GUI like virt-manager, and look at the resulting
config file

> How can one boot Arch Linux or any distro really without having that distro
> already running to copy the system from right?

Don't know about archilinux, but other distros can manage just fine.
The general method is to have a special kernel and initrd for
installation that is xen-compatible (like
http://mirrors.kernel.org/centos/5/os/x86_64/images/xen/), then
perform a network-based install (http, nfs, etc.)

> Is HVM install the only way?

No, but depending on your setup, it might be the easiest way.

-- 
Fajar

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